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Background and Goals

Vision in primates is an active process, in which the eyes go through a characteristic sequence of saccadic eye movements and fixations on stimuli in a visual scene. Recent evidence suggests that mice, despite lacking a foveal specialization for high acuity vision, use eye movements not only for image stabilization (Meyer et al., 2018; Wallace et al., 2013) but also for active sampling of natural scenes (Samonds et al., 2018). While saccadic eye movements are thus an integral part of visual perception, little is known about the consequences of saccades on population responses in visual cortex during and after the eye movement. In primate visual cortex (LIP), responses of single neurons just before saccade onset can shift from signaling targets in their normal receptive field (RF) to targets that the receptive field will occupy after the saccade (saccadic remapping; Duhamel et al., 1992). Furthermore, population responses should be enhanced after saccades, in particular if saccade sizes are large enough to shift novel visual input into individual RFs, as predicted by simulations of saccade and receptive field sizes during the processing of natural scenes (Samonds et al., 2018).

The proposed PhD project aims to directly measure the impact of saccadic eye movements on population activity in the visual cortex of mice during the processing of natural scenes in an immersive visual display using extracellular recordings with silicon probes. Computational inference methods will aid the project to reliably and automatically detect saccadic eye movements, and estimate where the mouse’s eyes are pointing. By testing predictions of neural responses before, during, and after saccades, we plan to assess potential non-linearities in the neuronal population response around the time of eye movements. Finally, after identifying signatures of saccadic eye movements in the population response, we plan to predict the occurrence of saccades based on the neuronal population response.